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Comparative analysis of long-term chlorophyll data with generalized additive model - San Francisco Bay and St. Lucie Estuary
Citation:
Wan, Y. AND M. Beck. Comparative analysis of long-term chlorophyll data with generalized additive model - San Francisco Bay and St. Lucie Estuary. CERF 24th Biennial Conference, Providence, RI, November 05 - 09, 2017.
Impact/Purpose:
It has been well recognized that nutrient pollution is one of the most widespread water quality problems facing the US. Excess nutrient exports from varying sources have been linked to a host of ecosystem impacts including eutrophication and hypoxia of downstream estuaries. Understanding the pathways of nutrient export from a watershed in relation to hydrology and watershed management is critical to the development of technically sound nutrient management strategies. This presentation compared nutrients export into two estuaries, Indian River Lagoon and San Francisco Bay, both of which have received considerable attention due to concerns of excessive nutrient loading. The presentation will cover analysis of long-term monitoring data with novel data synthesis methods. The research will support the “Nitrogen and Co-Pollutant Research Roadmap”, along with practical implication for local stakeholders in Florida and California.
Description:
The health of estuarine ecosystems is often influenced by hydraulic and nutrient loading from upstream watersheds. We examined four decades of monitoring data of nutrient export into the Indian River Lagoon and San Francisco Bay, both of which have received considerable attention due to concerns of excessive nutrient loading. The objective was to compare the temporal changes in nutrient export behavior in relation to hydrology and coastal zone management. While nutrient export, in general, exhibited chemodynamic regimes for both systems (nutrient concentrations change with discharge), a dilution effect of point sources dominated nutrient export for San Francisco Bay and flow-driven release for the Indian River Lagoon. Using generalized additive models (GAMs), we further explored the hydrological and watershed management controls on multi-decadal trends in nutrient concentrations along with hypothesis testing of additional factors related to nutrient export. These dynamic models revealed dynamic, non-linear changes in decadal and seasonal patterns, with GAMs for San Francisco Bay featuring distinct drought effects independent of long-term averages whereas models for Indian River Lagoon exhibiting short-term peaks associated with tropical activities.